Sealpot and method for controlling a solids flow rate therethrough

ABSTRACT

A sealpot for a combustion power plant includes a downcomer standpipe which receives solids of the combustion power plant, a bed including a first end and a second opposite end, the first end connected to the downcomer standpipe, a discharge standpipe disposed at the second opposite end of the bed, and an orifice plate disposed between the bed and the discharge standpipe separating the discharge standpipe from the bed. The orifice plate includes apertures disposed at a height above the bed which allow transport of fluidized solids and gas through the orifice plate.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 61/165,072, filed on Mar. 31, 2009, and all the benefitsaccruing therefrom under 35 U.S.C. §119, the content of which in itsentirety is/are herein incorporated by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

The U.S. Government has rights in this invention pursuant to ContractNo. DE-FC26-03NT41866 awarded by the U.S. Department of Energy.

TECHNICAL FIELD

The present disclosure relates generally to a sealpot and a method forcontrolling a flow rate therethrough. More particularly, the presentdisclosure relates to a sealpot including a multiple orifice exit designand a method for controlling a flow rate of solids through the sealpot.

BACKGROUND

Fluidized bed combustion (FBC) is a combustion technology used in powerplants, primarily to burn solid fuels. FBC power plants are moreflexible than conventional power plants in that they can be fired oncoal, coal waste or biomass, among other fuels. The term FBC covers arange of fluidized bed processes, including circulating fluidized bed(CFB) boilers, bubbling fluidized bed (BFB) boilers and other variationsthereof. In an FBC power plant, fluidized beds suspend solid fuels onupward-blowing jets of air during the combustion process in a combustor,causing a tumbling action which results in turbulent mixing of gas andsolids. The tumbling action, much like a bubbling fluid, provides ameans for more effective chemical reactions and heat transfer in thecombustor.

During the combustion process of fuels which have a sulfur-containingconstituent, e.g., coal, sulfur is oxidized to form primarily gaseousSO₂. In particular, FBC reduces the amount of sulfur emitted in the formof SO₂ by a desulfurization process. A suitable sorbent, such aslimestone containing CaCO₃, for example, is used to absorb SO₂ from fluegas during the combustion process. In order to promote both combustionof the fuel and the capture of sulfur, FBC power plants operate attemperatures lower than conventional combustion plants. Specifically,FBC power plants typically operate in a range between about 850° C. andabout 900° C. Since this allows coal to combust at cooler temperatures,NO_(x) production during combustion is lower than in other coalcombustion processes.

To further increase utilization of the fuel and efficiency of sulfurcapture, a cyclone separator is typically used to separate solids, e.g.,unutilized fuel and/or limestone, entrained in flue gas leaving thecombustor. The separated solids are then returned to the combustor via arecirculation means, e.g., a recirculation pipe, to be used again in thecombustion process. A sealpot, sometimes referred to as a “j-leg,”maintains a seal between the combustor and the cyclone separator toprevent unwanted escape of flue gas from the combustor backward, e.g.,in a direction opposite to flow of the separated solids into thecombustor, through the recirculation pipe.

Air systems in an FBC power plant are designed to perform manyfunctions. For example, air is used to fluidize the bed solidsconsisting of fuel, fuel ash and sorbent, and to sufficiently mix thebed solids with air to promote combustion, heat transfer and reduceemissions (e.g., SO₂, CO, NO_(x) and N₂O). In order to accomplish thesefunctions, the air system is configured to inject air, designatedprimary air (PA) or secondary air (SA), at various locations and atspecific velocities and quantities.

In addition, fluidizing air and transport air are typically supplied tothe sealpot to facilitate flow of solids and gas through the sealpot, asshown in FIG. 1. Referring to FIG. 1, a sealpot 10 of the prior artincludes a downcomer standpipe 15, a fluidizing/transport bed 20, afluidizing air source 25, a discharge standpipe 30, a transport airsource 35 and a weir 40 separating the fluidizing/transport bed 20 andthe discharge standpipe 30. The fluidizing/transport bed 20 includes afluidizing zone supplied with fluidizing air from the fluidizing airsource 25, and a transport zone supplied with transport air from thetransport air source 35. The fluidizing air source 25 and the transportair source 35 may be separate components, as shown in FIG. 1, or,alternatively, the fluidizing air source 25 and the transport air source35 may be combined as a single air source (not shown).

As shown in FIG. 1, in the sealpot 10 of the prior art, solids from thecombustion process flow downward from the cyclone separator (not shown)through the downcomer standpipe 15 to the fluidizing/transport bed 20.The solids are fluidized by the fluidizing air from the fluidizing airsource 25 and/or the transport air source 35 in the fluidizing zone ofthe fluidizing/transport bed 20. The fluidized solids are thentransported through the transport zone of the fluidizing/transport bed20 to the discharge standpipe 30 by the fluidizing air from thefluidizing air source 25 and/or the transport air supplied from thetransport air source 35, thereby forming an expansion bed in thedischarge standpipe 25. More specifically, solids which are transportedabove the weir 40, e.g., above a weir height H_(weir), form theexpansion bed, thereby causing some solids to flow over the weir 40 intothe discharge pipe 30. In addition, some gases, primarily fluidizing airfrom the fluidizing air source 25 and transport air from the transportair source 35, flow to the combustor via the discharge standpipe 30.Thus, the sealpot 10 forms a seal, thereby preventing flue gases in thecombustor from flowing backward through the sealpot 10, e.g., upwardthrough the downcomer standpipe 15 back into the cyclone (105 shown inFIG. 4).

In the sealpot 10 of the prior art, it is difficult to control a size ofthe expansion bed due to the nature of unsteady solid/gas interactions,particularly during transition of operations and resulting changes ingas and solids flow rate to the combustor (not shown) through thedischarge standpipe 30. As a result, an excessive amount of solids flowover the weir 40, e.g., the size of the sealpot expansion bed suddenlybecomes excessively large, which may disrupt the distribution of thefluidization air at the downstream combustor. In such a case,oscillation of pressure changes may occur in the system.

In addition, a range of flow rates of solids regulation through thesealpot 10 is limited in the sealpot 10 of the prior art, since the sizeof the expansion bed cannot be precisely regulated to control a numberof different flow rates of solids over the weir. Put another way, solidsare essentially either flowing over the weir or they are not; there areno precisely defined discrete flow rates and different flow rates aretherefore difficult to establish a steady continuous flow, especiallyduring transition of operations, as described above.

Accordingly, it is desired to develop a sealpot and a method forcontrolling a flow rate of solids through the sealpot, such that thesealpot has benefits including, but not limited to: increased solidsflow control range and accuracy of regulation thereof; increased steadystate seal maintainability; decreased flue gas escape; decreased solidssudden overflow; and increased turndown ratio of solids flow controlusing a sealpot.

SUMMARY

According to the aspects illustrated herein, there is provided a sealpotfor a combustion power plant. The sealpot includes a downcomer standpipewhich receives solids of the combustion power plant, a bed having afirst end and a second opposite end, the first end connected to thedowncomer standpipe, and a discharge standpipe disposed at the secondopposite end of the bed. An orifice plate is disposed between the bedand the discharge standpipe to separate the discharge standpipe from thebed. The orifice plate has a plurality of apertures disposed at a heightabove the bed and which allow transport of fluidized solids and gasthrough the orifice plate at a controlled rate.

According to the other aspects illustrated herein, there is provided amethod of maintaining a seal between a solids separator of a fluidizedbed combustion power plant and a combustor of the fluidized bedcombustion power plant. The method includes: connecting a downcomerstandpipe to the solids separator of the fluidized bed combustion powerplant; connecting a first end of a bed to the downcomer standpipe;disposing a discharge standpipe between a second opposite end of the bedand the combustor of the fluidized bed combustion power plant; anddisposing an orifice plate between the bed and the discharge standpipeseparating the discharge standpipe from the bed. The orifice plate has aplurality of apertures disposed at a height substantially above the bed,and the plurality of apertures allow transport of fluidized solids andgas through the orifice plate.

The above described and other features are exemplified by the followingfigures and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the figures, wherein the like elements are numberedalike:

FIG. 1 is a schematic side elevation view of a sealpot of the prior art;

FIG. 2 is a schematic side elevation view of a sealpot according to anexemplary embodiment of the present invention;

FIG. 3 is a schematic cross-section view, taken along line III-III′ ofFIG. 2, illustrating an orifice plate of the sealpot according to theexemplary embodiment of the present invention shown in FIG. 2; and

FIG. 4 is a schematic side elevation view of a fluidized bed combustionpower plant utilizing the sealpot of FIG. 2 according to an exemplaryembodiment of the present invention.

DETAILED DESCRIPTION

Disclosed herein are a sealpot and a method for controlling a flow ratetherethrough, and more specifically, a sealpot having an orifice plateand a method for controlling a flow rate of solids through the sealpot.

Referring to FIG. 2, a sealpot 100 according to an exemplary embodimentof the present invention includes a downcomer standpipe 15. Thedowncomer standpipe 15 receives solids from a solids separator (notshown) such as a cyclone separator 105 (in FIG. 4), for example, but isnot limited thereto in alternative exemplary embodiments. The downcomerstandpipe 15 supplies the solids to a fluidizing and/or transport bed 20of the sealpot 100. A fluidizing zone of the fluidizing/transport bed 20is supplied with a fluidizing gas, such as fluidizing air, for example,from a fluidizing air source 25. Alternatively (or additionally), atransport zone of the fluidizing/transport bed 20 is supplied with atransport gas, e.g., transport air, supplied from a transport air source35. The fluidizing air source 25 and the transport air source 35 may beseparate components, as shown in FIG. 2, or, alternatively, may beincluded in a single air source (not shown).

A discharge standpipe 30 of the sealpot 100 is connected to thefluidizing/transport bed 20 in an area substantially corresponding tothe transport zone of the fluidizing/transport bed 20. In addition, anorifice plate 110 is disposed between the discharge standpipe 30 and thefluidizing/transport bed 20, as shown in FIG. 2. The orifice plate 110has a plurality of apertures which limits solids and allows fluids beingtransported from the fluidizing/transport bed 20 to the dischargestandpipe 30.

The plurality of apertures of the orifice plate 110 is disposed at aheight above the fluidizing/transport bed 20, as shown in FIGS. 2 and 3.The plurality of apertures includes at least one solids aperture 210 andat least one gas aperture 220. In an exemplary embodiment, the solidsaperture 210 is located at a height below the gas aperture 220.Specifically, the solids aperture 210 is disposed below the gas aperture220 with respect to a portion of the discharge standpipe 30 throughwhich gas and solids flow to a combustor 300 (FIG. 4). Morespecifically, the solids aperture 210 is disposed at a height above aweir height H_(weir) and below a maximum bed expansion height, while thegas aperture 220 is disposed above the maximum bed expansion height(FIG. 3). As a result, fluidized solids maintained in thefluidizing/transport bed 20 act as a seal between the solids separator105 and the combustor 300.

Referring to FIG. 3, an exemplary embodiment includes a plurality ofaperture rows. The plurality of aperture rows includes a first aperturerow having at least one solids aperture 210 disposed above the weirheight H_(weir) and below the maximum bed expansion height, a secondaperture row having at least one solids aperture 210 disposed above thefirst aperture row and below the maximum bed expansion height, a thirdaperture row having at least one solids aperture 210 disposed above thesecond aperture row and below the maximum bed expansion height, and afourth aperture row having at least one gas aperture 220 disposed abovethe maximum bed expansion height. It will be noted that additionalexemplary embodiments are not limited to configuration described above,that there may be more or less than four aperture rows in an alternativeexemplary embodiment. Specifically, for example, another exemplaryembodiment may include first and second aperture rows having solidsapertures 210 disposed therein, and a third aperture row having gasapertures 220 disposed therein. Accordingly, total solids flow throughthe sealpot 100 according to an exemplary embodiment is equal to themaximum allowable flow through the particular sealpot 100.

Operation of the sealpot 100 according to an exemplary embodiment willnow be described in further detail with reference to FIGS. 2 and 3. Thedowncomer standpipe 15 receives solids, e.g., particulates from acombustion process, from the cyclone separator 105 (FIG. 4). The solidsflow downward in the downcomer standpipe 15, e.g., toward thefluidizing/transport bed 20. When the solids reach thefluidizing/transport bed 20, they mix with fluidizing air supplied fromthe fluidizing air source 25 and/or with transport air from thetransport air source 35 to form fluidized solids in the fluidizing zoneof the fluidizing/transport bed 20 (FIG. 2).

As a result, the fluidized solids, along with air from the fluidizingair source 25 and/or the transport air source 35, form an expansion bed.The expansion bed is forced upward out of the fluidizing/transport bed20 into the discharge standpipe 30, as shown in FIG. 2. Referring toFIG. 3, the expansion bed expands upward into a portion of the dischargestandpipe 30 towards the solids apertures 210 of the orifice plate 110.More specifically, when an expansion bed height H_(bed expansion) of theexpansion bed exceeds the weir height H_(weir), the expansion bed comesinto contact with the orifice plate 110. As the expansion bed heightH_(bed expansion) further increases, the expansion bed is exposed to thesolids apertures 210, and solids thereby flow through the solidsapertures 210 and downward to the combustor 300 (FIG. 4) through theexposed solids aperture(s) 210. As solids flow exceed the limit of eachrow of solids apertures 210, the solids will expand upward further untilit reaches the next highest row of solids apertures 210. Solids flow isthereby regulated based on the number and arrangement of row of solidsapertures 210 in addition to the fluidizing/transport gas supplied.

Gas in the expansion bed, e.g., the air supplied from the fluidizing airsource 25 and/or the transport air source 35, also flows upward into thedischarge standpipe 30 as the solids flow through the solids apertures210 of the orifice plate 110. The upward flowing gas then flows throughthe gas aperture 220 towards the combustor 300.

Thus, both the gas flowing through the gas aperture 220 and the solidsflowing through the solids apertures 210 flow downward, e.g., towardsthe combustor 300 (FIG. 4) and are thereby delivered back to thecombustor 300.

In an exemplary embodiment, a flow rate of solids through the sealpot100 is based upon a velocity of the fluidizing air and/or the transportair supplied from the fluidizing air source 25 and/or the transport airsource 35, respectively. In general, the flow of solids is related tothe velocity of the fluidizing air and/or the transport air, e.g.,increasing the velocity of the fluidizing air and/or the transport aircauses a corresponding increase in the flow rate of solids through thesealpot 100 (via more exposed solids apertures 210, as discussed ingreater detail above). Therefore, a desired flow rate of solids, basedupon operation of a power plant (not shown) having the sealpot 100, ismaintained by adjusting the velocity of the fluidizing air and/or thetransport air.

In an alternative exemplary embodiment, the flow rate of solids throughthe sealpot 100 is based upon a total number of solids apertures 210 incontact with, e.g., exposed to, the solids such that the solids can flowthrough the solids apertures 210. More specifically, the flow rate ofsolids is substantially proportional to the total number solid apertures210 exposed to the solids; increasing the total number of solidsapertures 210 exposed to the solids increases the flow rate of solidsthrough the sealpot 100. Therefore, the desired flow rate of solids,based upon operation of a power plant (not shown) having the sealpot, ismaintained by adjusting the bed expansion height through the totalnumber of solids apertures 210.

In yet another alternative exemplary embodiment, the flow rate of solidsthrough the sealpot 100 is based upon an opening diameter of at leastone of the solids apertures 210. Specifically, the flow rate of solidsis substantially proportional to the diameter of a given solid apertures210. More specifically, increasing the diameter of the solids aperture210, and thereby increasing a cross-sectional area of the solidsaperture 210 through which solids can flow, increases the flow rate ofsolids through the sealpot 100. Therefore, the desired flow rate andflow range of solids, based upon operation of a power plant (not shown)having the sealpot 100, is maintained by adapting the diameter of thesolids aperture 210. Further, alternative exemplary embodiments mayinclude individual solids apertures 210 having different diameters,e.g., diameters of each solids aperture 210 need not be equal. Inaddition, a cross-sectional shape of the solids aperture 210 accordingto an exemplary embodiment is substantially oval, as shown in FIG. 3,but alternative exemplary embodiments are not limited thereto, but mayinstead be varied to adjust the flow rate of solids through the sealpot100. For example, the cross-sectional shape of the solids aperture 210according to alternative exemplary embodiments may be, for example,circular, rectangular, square, triangular, polygonal or a combinationthereof.

In still another alternative exemplary embodiment, the flow rate ofsolids through the sealpot 100 is based upon a height of a bed expansionline of relative to heights of the solids apertures 210. Morespecifically, the flow rate of solids is proportional to the height ofthe solid apertures 210 above the fluidizing/transport bed 20;increasing the height of the bed expansion using the solids apertures210 increases the flow rate of solids through the sealpot 100, forexample. Therefore, the desired flow rate of solids, based uponoperation of a power plant (not shown) having the sealpot, is maintainedby adjusting the height of the bed expansion using the solids apertures210 above the fluidizing/transport bed 20.

Thus, a range of solids flow rates is substantially increased oreffectively maximized in the sealpot 100 according to an exemplaryembodiment by varying the velocity of the fluidizing air and/or thetransport air, the total number of solids apertures 210, a diameter ofeach of the solids apertures 210 and/or a height of each of the solidsapertures 210. In addition, varying the attributes of the sealpot 100described above further provides an advantage of precise control overthe improved range of solids flow rates. It should be noted thatalternative exemplary embodiments are not limited to the aforementionedmethods of controlling the solids flow rate; rather, alternativeexemplary embodiments may employ any of, all of, or any combination ofthe methods described herein, but are not limited thereto. Moreover, itwill be noted that the present invention is not limited to powercombustion, but may instead be utilized with any solidsdistribution/transport/other sealpot applications.

In an exemplary embodiment with respect to FIG. 4, a solids controlvalve 205 (FIG. 4) may be connected to the fluidizing/transport bed 20at an area of the fluidizing/transport bed 20 substantially opposite tothe area substantially corresponding to the transport zone of thefluidizing/transport bed 20.

The solids control valve 205 (FIG. 4) causes a predetermined portion ofthe fluidized solids in the fluidizing zone of the fluidizing/transportbed 20 to bypass the discharge standpipe 30. For example, a portion ofthe fluidized solids may be returned to the combustor 300 beforereaching the transport zone of the fluidizing/transport bed 20, as willbe described in greater detail below with reference to FIG. 4. Thesolids control valve 205 may, however, be omitted from alternativeexemplary embodiments, or may be replaced with other components, such asa pressure seal (not shown) or control valve (not shown), for example,but is not limited thereto.

Referring to FIG. 4, combustion power plant 310 and, more particularly,a fluidized bed combustion (FBC) power plant 310 includes the combustor300, the solids separator 105, e.g., the cyclone separator 105, and thesealpot 100 according to an exemplary embodiment. The furnace 300 of theFBC power plant is supplied with primary air (PA) 315, secondary air(SA) 320 and fuel 325. In addition, other materials such as limestone(not shown), for example, may be supplied to the furnace 300, butalternative exemplary embodiments are not limited to the foregoingcomponents or materials.

In an exemplary embodiment, the combustor 300 is an FBC-type combustorsuch as a circulating fluidized bed (CFB) combustor, but alternativeexemplary embodiments are not limited thereto. For example, thecombustor 300 may be a bubbling fluidized bed (BFB) combustor, a movingfluidized bed combustor or a chemical looping combustor.

As the combustor 300 burns the fuel 325, combustion products, includinggases and solids, exit the combustor 300 via a flue 330 and enter thecyclone separator 105. The cyclone separator 105 separates the solidsand supplies the solids to the downcomer standpipe 15 of the sealpot100. The gases exit the cyclone separator 105 via a central duct 335 andare delivered to other components of the FBC power plant 310 such asatmosphere control equipment (not shown) via a tangential duct 340.

The solids separated by the cyclone separator 105 are delivered to thedowncomer standpipe 15 of the sealpot 100. In an exemplary embodiment,the solids are then returned to the combustor 300 via the dischargestandpipe 30 of the sealpot 100, as described above in greater detailwith reference to FIGS. 2 and 3.

In an alternative exemplary embodiment, the solids control valve 205redirects a predetermined portion of fluidized solids in the fluidizingzone of the fluidizing/transport bed 20 of the sealpot 100 are directedto a fluidized bed heat exchanger 350 through a fluidized bed heatexchanger inlet pipe 360. The redirected fluidized solids pass throughthe fluidized bed heat exchanger 350 and are then supplied to thecombustor 300 through a fluidized bed heat exchanger outlet pipe 370, asshown in FIG. 4. The solids control valve 205, the fluidized bed heatexchanger inlet pipe 360, the fluidized bed heat exchanger 350 and thefluidized bed heat exchanger outlet pipe 370 may be omitted inalternative exemplary embodiments.

Furthermore, alternative exemplary embodiments are not limited to thosedescribed herein. For example, a method of maintaining a seal betweenthe solids separator 105 and the combustor 300 of the FBC power plant310 of FIG. 4 according to an alternative exemplary embodiment includesconnecting the downcomer standpipe 15 of the sealpot 100 to the solidsseparator 105, connecting the fluidizing/transport bed 20 of the sealpot100 to the downcomer standpipe 15, and connecting the dischargestandpipe 30 having the orifice plate 110 therein between thefluidizing/transport bed 20 and the combustor 300.

The method further includes receiving solids from the solids separator105 into the downcomer standpipe 15, fluidizing the solids using airsupplied from the fluidizing air source 25 (FIG. 2), and/or transportingthe fluidized solids to the discharge standpipe 30 using air suppliedfrom the transport air source 35 (FIG. 2), receiving the fluidizedsolids from the fluidizing/transport bed 20 into the discharge standpipe30, receiving the air supplied from the fluidizing air source 25 and theair supplied from the transport air source 35 into the dischargestandpipe 30, and delivering the fluidized solids, the air supplied fromthe fluidizing air source 25 and the air supplied from the transport airsource 35 to the combustor 300 through the discharge standpipe 30through the plurality of apertures of the orifice plate 110. The presentinvention contemplates that the flow rate of the fluidized solidstransported to the discharge standpipe 30 is controlled based upon atleast one of a diameter (e.g., cross-sectional area) of the solidsapertures 210, a shape of the solids apertures 210, a total number ofthe solids apertures 210, a height of the solids apertures 210 and/or aflow rate of the air supplied from the transport air source 35.

Thus, a sealpot according to an exemplary embodiment provides a multipleorifice exit design and a method for controlling a flow rate of solidsthrough the sealpot. Therefore, the sealpot has a substantiallyincreased or effectively improved solids flow control range, as well asincreased precision of regulation of the solids flow control range.

In addition, the sealpot has increased steady state sealmaintainability, decreased flue gas escape, decreased solids overflowand increased turndown ratio.

It will be noted that while exemplary embodiments have been describedwith reference to a sealpot associated with fluidized bed combustionpower plants such as circulating fluidized bed boilers and chemicallooping reactors, alternative exemplary embodiments are not limitedthereto. Rather, a sealpot according to alternative exemplaryembodiments may be utilized in any type of power plant including, butnot limited to, bubbling fluidized bed boilers and other variations offluidized bed combustion power plants, as well as conventional powerplants.

In addition, it will be noted that, while a single sealpot has beendescribed herein, the present invention contemplates that a plurality ofthe sealpots may be included, such that the plurality of sealpotsreceive solids flow from a common downcomer standpipe and distributefluidized solids and gas to various components and/or locations via anumber of discharge standpipes corresponding to each of the sealpots.Thus, flow rates and other parameters for each of the associatedfluidized solids/gas flow may be controlled based on the individualcharacteristics, discussed in greater detail above, of each particularsealpot. While the sealpot has been described to control the process ofa power plant, the present invention contemplates that the sealpot maybe used with any process needing to control solids flow and/or pressurewithin such a system.

While the invention has been described with reference to variousexemplary embodiments, it will be understood by those skilled in the artthat various changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

What is claimed is:
 1. A sealpot for a combustion power plant, thesealpot comprising: a downcomer standpipe having an upper end, whichreceives solids of the combustion power plant, and lower end; a bedhaving a first end and a second opposite end, the first end of the bedreceiving particles fluidly connected to the lower end of the downcomerstandpipe to provide the solids to the bed; a discharge standpipefluidly connected to the second opposite end of the bed; and an orificeplate disposed at the second opposite end of the bed and disposedbetween the bed and the discharge standpipe, separating the dischargestandpipe from the bed, the orifice plate having a plurality ofapertures disposed at a height above the bed, the plurality of aperturesallowing transport of fluidized solids and gas through the plurality ofapertures of the orifice plate from the bed to the discharge standpipe.2. The sealpot according to claim 1, wherein the downcomer standpipereceives the solids from a solids separator, the bed receives the solidsfrom the downcomer standpipe at the first end of the bed, fluidizes thesolids using a gas, and transports the fluidized solids and the gas tothe second end of the bed through the apertures of the orifice plate tothe discharge standpipe, and the discharge standpipe receives thefluidized solids and the gas from the bed through the plurality ofapertures of the orifice plate and delivers the fluidized solids and thegas to the combustion power plant.
 3. The sealpot according to claim 1,wherein the combustion power plant comprises at least one of a fluidizedbed combustion power plant, a circulating fluidized bed boiler, abubbling fluidized bed boiler, a moving fluidized bed boiler and achemical looping combustor.
 4. The sealpot according to claim 1, whereinthe plurality of apertures comprises a solids aperture and a gasaperture disposed at a height above the solids aperture.
 5. The sealpotaccording to claim 4, wherein the solids aperture is disposed at aheight above a weir height and below a maximum bed expansion height. 6.The sealpot according to claim 5, wherein the gas aperture is disposedat a height above the maximum bed expansion height.
 7. The sealpotaccording to claim 1, wherein the orifice plate extends from a bottomportion defining the bed and extends to a height substantially above thebed.
 8. The sealpot according to claim 1, wherein the gas whichfluidizes the solids in the bed includes air supplied from a fluidizingair source, the fluidized solids are transported to the dischargestandpipe using air supplied from a transport air source, and a flowrate of the fluidized solids transported to the discharge standpipe iscontrolled based on at least one of, a total number of the plurality ofapertures, a diameter of an aperture of the plurality of apertures, across-sectional shape of an aperture of the plurality of apertures, anarea of an aperture of the plurality of apertures and a height of anaperture of the plurality of apertures.
 9. The sealpot according toclaim 8, wherein the flow rate of the fluidized solids is furthercontrolled based on a flow rate of the air supplied from the fluidizingair source.
 10. The sealpot according to claim 1, wherein the gas whichfluidizes the solids in the bed includes air supplied from a fluidizingair source, the fluidized solids are transported to the dischargestandpipe using air supplied from a transport air source, and a range offlow rates of the fluidized solids transported to the dischargestandpipe is controlled based on at least one of a total number of theplurality of apertures, a diameter of an aperture of the plurality ofapertures, a cross-sectional shape of an aperture of the plurality ofapertures, an area of an aperture of the plurality of apertures and aheight of an aperture of the plurality of apertures.
 11. The sealpotaccording to claim 1, further comprising a solids control valve fluidlyconnected to the first end of the bed, wherein the solids control valvecontrols a flow rate of solids to the combustion power plant bypassingthe sealpot.
 12. The sealpot according to claim 1, wherein the pluralityof apertures comprises: a first aperture row having at least one solidsaperture; a second aperture row having at least one solids aperture; anda third aperture row having at least one gas aperture, wherein the firstaperture row is disposed at a height above a weir height and below amaximum bed expansion height, the second aperture row is disposed at aheight above the first aperture row and below the maximum bed expansionheight, and the third aperture row is disposed at a height above themaximum bed expansion height.
 13. The sealpot according to claim 1,wherein the bed includes at least one of a fluidizing bed and atransport bed.
 14. The sealpot according to claim 1, further comprisinga plurality of sealpots to enable the fluidized solids and gas from thedowncomer standpipe to be transported to corresponding dischargestandpipes of each of the sealpots, wherein each of the sealpots includea orifice plate having a plurality of apertures disposed between eachrespective bed and discharge standpipe.
 15. A method of maintaining aseal between a solids separator of a combustion power plant and acombustor of the combustion power plant, the method comprising:connecting an upper end of a downcomer standpipe to the solids separatorof the combustion power plant; connecting a first end of a bed to alower end of the downcomer standpipe; disposing a discharge standpipe ata second opposite end of the bed; and disposing an orifice plate at thesecond opposite end of the bed and disposed between the bed and thedischarge standpipe separating the discharge standpipe from the bed, theorifice plate having a plurality of apertures disposed at a height abovethe bed, the plurality of apertures allowing transport of fluidizedsolids and gas through the orifice plate.
 16. The method of claim 15,further comprising: receiving solids from the solids separator in thedowncomer standpipe; receiving the solids from the downcomer standpipein the bed at the first end of the bed; fluidizing the solids using agas; transporting the fluidized solids and the gas through the orificeplate to the discharge standpipe at the second end of the bed; receivingthe fluidized solids and the gas from the bed in the discharge standpipethrough apertures of the plurality of apertures; and delivering thefluidized solids and the gas to the combustor, wherein a flow rate ofthe fluidized solids transported to the discharge standpipe iscontrolled based on at least one of a flow rate of the gas, a totalnumber of the plurality of apertures, a diameter of an aperture of theplurality of apertures, a cross-sectional shape of an aperture of theplurality of apertures, an area of an aperture of the plurality ofapertures and a height of an aperture of the plurality of apertures. 17.The method of claim 15, wherein the combustion power plant comprises atleast one of a fluidized bed combustion power plant, a circulatingfluidized bed boiler, a bubbling fluidized bed boiler, a movingfluidized bed boiler and a chemical looping combustor.
 18. The method ofclaim 15, wherein the plurality of apertures comprises a solids aperturedisposed at a height above a weir height and below a maximum bedexpansion height.
 19. The method of claim 18, wherein the plurality ofapertures further comprises a gas aperture is disposed at a height abovethe maximum bed expansion height.
 20. The method of claim 18, whereinthe bed includes at least one of a fluidizing bed and a transport bed.21. A sealpot comprising: an input pipe having an upper end, whichreceives solids, and a lower end; a bed having a first end and a secondopposite end, the first end of the bed fluidly connected to the lowerend of the input pipe to provide the solids to the bed, wherein thesolids are fluidized; a discharge pipe fluidly connected to the secondopposite end of the bed for removing the fluidized solids from the bed;and an orifice plate disposed plate at the second opposite end of thebed and disposed between the bed and the discharge pipe separating thedischarge pipe from the bed, the orifice plate having a plurality ofapertures disposed at a height above the bed, the plurality of aperturesallowing transport of the fluidized solids and gas through the orificeplate from the bed to the discharge standpipe.
 22. The sealpot accordingto claim 21, wherein the plurality of apertures comprises a solidsaperture and a gas aperture disposed at a height above the solidsaperture.
 23. The sealpot according to claim 22, wherein the solidsaperture is disposed at a height above a weir height and below a maximumbed expansion height.
 24. The sealpot according to claim 23, wherein thegas aperture is disposed at a height above the maximum bed expansionheight.
 25. The sealpot according to claim 21, wherein the gas whichfluidizes the solids in the bed includes air supplied from a fluidizingair source, the fluidized solids are transported to the discharge pipeusing air supplied from a transport air source, and a flow rate of thefluidized solids transported to the discharge pipe is controlled basedon at least one of a total number of the plurality of apertures, adiameter of an aperture of the plurality of apertures, a cross-sectionalshape of an aperture of the plurality of apertures, an area of anaperture of the plurality of apertures and a height of an aperture ofthe plurality of apertures.
 26. The sealpot according to claim 21,wherein the gas which fluidizes the solids in the bed includes airsupplied from a fluidizing air source, the fluidized solids aretransported to the discharge pipe using air supplied from a transportair source, and a range of flow rates of the fluidized solidstransported to the discharge pipe is controlled based on at least one ofa total number of the plurality of apertures, a diameter of an apertureof the plurality of apertures, a cross-sectional shape of an aperture ofthe plurality of apertures, an area of an aperture of the plurality ofapertures and a height of an aperture of the plurality of apertures. 27.The sealpot according to claim 21, wherein the plurality of aperturescomprises: a first aperture row having at least one solids aperture; asecond aperture row having at least one solids aperture; and a thirdaperture row having at least one gas aperture, wherein the firstaperture row is disposed at a height above a weir height and below amaximum bed expansion height, the second aperture row is disposed at aheight above the first aperture row and below the maximum bed expansionheight, and the third aperture row is disposed at a height above themaximum bed expansion height.